JP2000094615A - White laminated polyster film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white laminated polyester film which shows excellent bluish whiteness and smoothness. SOLUTION: This white laminated polyester film is composed of at least, two layers of a white polyester layer (A) and a white polyester layer (B), and has at least one projecting inflexion between 350-500 nm in curve of degree of total ray reflectivity, in the range of 350-700 nm measured from the white polyester layer (A) side, a peak reflectivity at the position of the inflexion point, is larger than the average reflectivity at least by 5% in the range of 500-700 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a white laminated polyester film.

More specifically, the present invention relates to a white laminated polyester film which is excellent in bluish whiteness and smoothness and is suitable as a base material of a receiving sheet used for various printing records such as ink jet, thermal transfer and offset printing.

[0003]

2. Description of the Related Art Conventionally, white polyester films containing inorganic fine particles such as titanium oxide, calcium carbonate, barium sulfate and the like in a polyester and a resin incompatible with the polyester have been used for various applications, particularly for ink jet,
It is applied to the base material of the receiving sheet as a printing record application such as thermal transfer and offset printing. Furthermore, in recent years, the accuracy of print records has been improved, and the sharpness of printed matter has been increased,
There is a demand for a white polyester film having a high whiteness and giving a higher quality.

[0004] In order to meet such demands, a combination of a plurality of the above-mentioned inorganic fine particles, a combination of an inorganic fine particle and an immiscible resin, or a combination of a fluorescent brightener and a fluorescent whitening agent are added. Etc. are known. Examples of such a white polyester film include, for example, JP-A No.
Japanese Unexamined Patent Application Publication No. 3232 and Japanese Unexamined Patent Application Publication No. 6-322153 are disclosed.

[0005]

However, when the above-mentioned white polyester film is used as a base material for a marking film, a poster or the like, not only the whiteness indicating "whiteness" is insufficient, but also the so-called "blue" Taste ”, specifically, the bluish index (color tone b value) represented as b of the color difference Lab defined in JIS K-7105 is not sufficient, so that the original color of the printed document, especially human skin or fruit There is a problem that it is not possible to express subtle and lively colors of vegetables and the like.

In addition, when the addition amount of inorganic fine particles or incompatible resin is increased in order to improve whiteness and blueness,
Used as a base material for receiving sheets that require not only the glossiness due to the film surface being rough and the smoothness being reduced, but also the whiteness and luxurious feeling, as well as the thermal transfer, such as thermal transfer. In some cases, the printing surface may become uneven or chipped, making it unusable.

[0007] Further, there is another problem that the film forming property is reduced and the film is frequently torn, thereby increasing the manufacturing cost.

In addition, for example, when an attempt is made to improve the bluish color by increasing the amount of the fluorescent whitening agent to be added, the coloring problem due to the fluorescent whitening agent and the printing function of the white polyester film are improved. When a receiving layer is provided according to the printing method, the adhesion between the receiving layer and the film surface is reduced,
Alternatively, there has been a problem that various problems such as a rise in raw material costs are likely to occur.

For this reason, the prior art cannot satisfy the above-mentioned requirements.

[0010] The present invention solves the above problems,
It is an object of the present invention to provide a white laminated polyester film which is excellent in “bluish whiteness” satisfying whiteness and blueness index and also excellent in smoothness.

[0011]

The white laminated polyester film of the present invention that achieves this object is a white laminated polyester film having at least two white polyester layers (A) and (B). 350 measured from the white polyester layer (A) side
In the total light reflectance curve in the range of ~ 700 nm, 35
It has at least one convex inflection point between 0 and 500 nm, and the peak reflectance at the position of the inflection point is 500-70.
A white laminated polyester film characterized by having an average reflectance of at least 5% higher than the average reflectance in the range of 0 nm.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The white laminated polyester film of the present invention will be described below.

In the present invention, the polyester is a polymer obtained by condensation polymerization of a diol and a dicarboxylic acid. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, and adipic acid. , Sebacic acid and the like, and the diol is represented by ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexanedimethanol and the like. Specifically, for example, polyethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene-
2,6-naphthalenedicarboxylate (polyethylene naphthalate) and the like can be used.

Of course, these polyesters may be homopolyesters or copolyesters. Examples of copolymerization components include diol components such as diethylene glycol, neopentyl glycol and polyalkylene glycol, adipic acid, Sebacic acid, phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid,
A dicarboxylic acid component such as 5-sodium sulfoisophthalic acid can be used. Further, in this polyester, if necessary, appropriate additives in an amount within a range that does not impair the effects of the present invention, for example, heat stabilizers, oxidation stabilizers, ultraviolet absorbers, weather stabilizers, Organic lubricant, organic fine particles, filler, antistatic agent, nucleating agent, dye, dispersant,
A coupling agent or the like may be blended.

As the polyester used in the present invention, polyethylene terephthalate and polyethylene naphthalate are preferred because they are excellent in water resistance, durability, chemical resistance and the like.

The white laminated polyester film in the present invention is a white laminated polyester film having at least two layers having at least a white polyester layer (A) and a white polyester layer (B).
In the total light reflectance curve in the range of 350 to 700 nm measured from the side, at least one convex inflection point is present between 350 to 500 nm, and the peak reflectance at the position of the inflection point is 500 to 500 nm. 5 from the average reflectance in the range of 700 nm
% Or more.

The peak reflectance is 500 to 700 n
Preferably, it is at least 7% higher than the average reflectance in the range of m, and most preferably at least 10% higher. If the peak reflectance is less than the average reflectance in the range of 500 to 700 nm or the difference is less than 5%, the bluish color is insufficient and the printed matter is inferior in clarity and luxury, and sometimes has a yellowish hue. May be. Here, "convex inflection point"
Means that the total light reflectance curve between 350 and 500 nm has an “upwardly convex shape”, and is not particularly limited as long as it is “upwardly convex shape”. 7
When the average reflectance in the range of 00 nm is used as the reference line, the larger the area occupied by the total light reflectance curve having the “upward convex shape”, the better the bluish whiteness is. preferable.

When there are two or more "convex inflection points", the inflection point having the highest reflectance value is determined as the peak reflectance. The upper limit of the difference in reflectance is not particularly limited, but it is needless to say that a larger value is preferable.

In the present invention, the average reflectance in the range of 500 to 700 nm measured from the white polyester layer (A) side is preferably 85% or more, more preferably 90%.
More preferably, it is the above. The average reflectance is 85%
If it is smaller, the whiteness is insufficient and the whiteness of the image is low, so that the “appearance” of the printed image is reduced and the image clarity tends to be poor.

The white polyester layer (A) in the present invention
And, those containing a white dye or inorganic fine particles in a layer made of polyester, or generate a myriad of fine bubbles in the layer, and scattered light by these fine bubbles to make it white and opaque Layers. Among the whitening methods, it is preferable to add inorganic fine particles to the polyester in terms of the smoothness (or gloss) of the film surface and the optical density.

As the inorganic fine particles, titanium oxide, zinc oxide, zinc carbonate, calcium carbonate, magnesium carbonate,
Magnesium oxide, silica, talc, kaolin, lithium fluoride, calcium fluoride, barium sulfate, zinc sulfide, alumina, calcium phosphate, mica, and the like can be used. These may be used alone or in combination of two or more.

In the present invention, among these particles,
In particular, from the viewpoint of comprehensive effects such as whiteness and optical density, it is more preferable to use titanium oxide, calcium carbonate, and barium sulfate, and titanium oxide is particularly preferable. Further, the inorganic fine particles may be in a form such as porous or hollow porous, and furthermore, within a range where the effect of the present invention is not impaired, in order to improve dispersibility in a resin, Processing or the like may be performed.

In the present invention, the average particle diameter of the inorganic fine particles is preferably from 0.05 to 3 μm, more preferably from 0.07 to 1 μm. If the average particle diameter is outside the above range, uniform dispersion becomes difficult, the smoothness of the film surface is deteriorated, and further, whiteness, bluishness, glossiness may be reduced due to these. It is not preferable. The addition amount of the inorganic fine particles is not particularly limited, but is preferably 1 to 35% by weight, more preferably 3 to 30% by weight, and most preferably 5 to 25% by weight. If the amount is less than the above range, it is difficult to improve the properties of the film, such as whiteness and optical density. Conversely, if the amount is more than the above range, the film may be broken during stretching or may have poor powder during post-processing. It may cause inconvenience such as occurrence.

The white laminated polyester film of the present invention needs to have a laminated structure of two or more layers having at least a white polyester layer (A) and a white polyester layer (B).

For example, when the effect of the present invention is intended to be obtained by a single-layer single film, whiteness, bluishness, glossiness,
It is very difficult to satisfy all properties such as hiding properties (optical density). Further, even if all the characteristics can be satisfied, the raw material cost increases, or the film forming property becomes unstable, resulting in an increase in the manufacturing cost. Therefore, the white polyester layer (A) has a laminated structure of two or more layers, and exhibits various properties such as whiteness, bluishness, and glossiness in the white polyester layer (A). And / or by forming a layer having properties other than the above-mentioned properties, it becomes possible to satisfy all the necessary properties as the whole white laminated polyester film.

In the present invention, at least the white polyester layer (A) contains a fluorescent whitening agent in order to give the white laminated polyester film a more vivid and bluish whiteness and to give a high quality image. Is desirable.

In the present invention, the fluorescent whitening agent is a polymer that absorbs ultraviolet light in sunlight or artificial light, converts the ultraviolet light into visible light of violet to blue, and radiates it. A compound that promotes whiteness and bluish color without reducing the lightness of the substance.

[0028] Examples of the fluorescent whitening agent include trade names "Ubitek" (Ciba-Geigy), "OB-1" (Eastman), "TBO" (Sumitomo Seika Co., Ltd.) and "Kay Coal".
(Nippon Soda Co., Ltd.), "Kayalite" (Nippon Kayaku Co., Ltd.), "Ryukopua" EGM (Client Japan Co., Ltd.) and the like can be used.

The fluorescent whitening agent is not particularly limited, and it may be used alone or in combination of two or more in some cases. It is desirable to select a resin which has good compatibility with the polyester, can be uniformly dispersed, has little coloring, and does not adversely affect the resin.

The content of the fluorescent whitening agent in the white polyester layer (A) is preferably 0.005 to 1% by weight,
Those in the range of 0.01 to 0.5% by weight are more preferred. If the content is less than the above range, it is difficult to obtain a sufficient whitening effect, and if the content exceeds the above range, a decrease in uniform dispersibility,
It tends to cause a decrease in the whitening effect called so-called "density quenching" or a decrease in whiteness due to coloring.

In order to further improve the bluish whiteness, the white polyester layer (A) and the white polyester layer (B) contain a fluorescent whitening agent, and the white polyester layer (A It is desirable that the content (% by weight) of the fluorescent whitening agent in ()) is larger than that in the white polyester layer (B). If the content is less than that in the white polyester layer (B), not only is there a problem that the effect of improving the bluish whiteness is low, but also the raw material cost tends to rise, which is not preferable. In the above case, the difference in the content of the fluorescent whitening agent between the white polyester layer (A) and the white polyester layer (B) is preferably 0.005 to 0.995% by weight, more preferably 0.01 to 0.95%. 7% by weight, most preferably 0.02 to 0.5% by weight. When the difference in the content is less than the above range, the effect when the configuration is different from that of the content is small, and as a result, the cost due to the multilayer configuration may increase. On the other hand, if the difference in the content is larger than the above range, the content of the fluorescent whitening agent in the white polyester layer (A) increases, which tends to cause a decrease in uniform dispersibility and a decrease in whiteness due to coloring. Is not preferred.

The white laminated polyester film of the present invention has a laminated structure of at least two layers having at least a white polyester layer (A) and a white polyester layer (B). The layer containing fine particles and the white polyester layer (B) as a layer containing fine bubbles gives flexibility and cushioning property when used as a base material of a receiving sheet such as ink jet or thermal transfer. To improve printability and transferability,
This is more preferable in reducing the weight of the substrate.

As a method for incorporating fine bubbles,
In general, a method of adding a foaming agent or fine particles and / or adding a thermoplastic resin incompatible with polyester and uniaxially or biaxially stretching the same to generate fine air bubbles is effective. Alternatively, it is preferable to use a thermoplastic resin incompatible with polyester from the viewpoint of film formation stability.

The thermoplastic resin referred to in the present invention is a thermoplastic resin other than polyester, and is preferably a resin incompatible with polyester. Such a resin is
In a measurement using a differential scanning calorimeter (DSC) or the like, a glass transition temperature (hereinafter, referred to as “Tg”) corresponding to polyester in a system in which polyester and the thermoplastic resin are melted.
Tg corresponding to the thermoplastic resin is observed in addition to the above.

The thermoplastic resin which is incompatible with the polyester has a great effect of dispersing in a particle form in the polyester and forming voids in the polyester film by stretching.

The melting point of such a thermoplastic resin is preferably lower than the melting point of the polyester and higher than the temperature used to orient the film support. From this point, among thermoplastic resins, olefin-based polymers such as polyethylene, polypropylene, polybutene, and polymethylpentene or copolymers thereof are preferable.

Among them, polypropylene and polymethylpentene having a small critical surface tension are preferable, and polymethylpentene is particularly preferable because it has a large surface tension difference from polyester and has a high melting point, so that it is easy to form fine bubbles during stretching. .

Further, when an olefin polymer or copolymer having a polar group such as a carboxyl group or an epoxy group, or a functional group reactive with polyester, a polyalkylene glycol, or the like is used in combination with the thermoplastic resin, The dispersion diameter of the plastic resin is reduced, and thus the voids formed by stretching can be made finer, and the film forming stability is improved.
It is preferable because the optical density is further improved.

The content of the thermoplastic resin incompatible with the polyester in the white polyester layer (B) is not particularly limited, but is preferably from 1 to 35% by weight, more preferably from 3 to 25% by weight. preferable. If the addition amount is less than the above range, the effect of weight reduction is small, and it is difficult to improve the properties of the film such as whiteness and optical density.

On the other hand, if the amount is larger than the above range, there may be a problem such as tearing of the film at the time of stretching.

In the present invention, the white polyester layer (A) and the white polyester layer (B) contain a polyester resin and inorganic fine particles as main components, and the white polyester layer (A) contains inorganic fine particles. Amount (% by weight)
Is smaller than that in the white polyester layer (B), which is more preferable in terms of improving film forming properties, smoothness (or glossiness) of the film surface, or reducing costs. In this case, the difference in the content of the inorganic fine particles between the white polyester layer (A) and the white polyester layer (B) is 2
It is preferably from 34 to 34% by weight, more preferably from 3 to 30% by weight, most preferably from 5 to 25% by weight. When the difference in the content is less than the above range, the effect when the configuration is different from that of the content is small, and as a result, the cost due to the multilayer configuration may increase. On the other hand, when the difference in the content is larger than the above range, the content of the inorganic fine particles in the white polyester layer (B) increases, and the film is easily broken at the time of stretching, and as a result, the cost increases. It is not preferable because of the tendency.

In the present invention, each of the white polyester layer (A) and the white polyester layer (B) may be the same polyester composition or different polyester compositions. Especially different polyester compositions,
For example, when the white polyester layer (B) is a homopolyester and the white polyester layer (A) is a copolyester, it is more preferable because characteristics such as easy adhesion can be obtained. Further, when the polyester used for the white polyester layer (A) is polyethylene naphthalate and the polyester used for the white polyester layer (B) is polyethylene terephthalate, it is preferable because effects of improving weather resistance, rigidity and the like can be obtained.

Further, the white laminated polyester film of the present invention is obtained by laminating a white polyester layer (A) on both sides of a white polyester layer (B) to form a three-layer laminated structure.
It is more desirable from the viewpoint of improving characteristics such as whiteness and blue tint and practicality.

In the present invention, the method of laminating the white polyester layer (A) and the white polyester layer (B) may be a method of co-extrusion during melt film formation, or a method of separately forming each film. Any of laminating methods may be used, but the former method is more preferable in terms of cost and the like.

The white laminated polyester film of the present invention has a whiteness of 8 determined from the white polyester layer (A) side.
Those having 0% or more, more preferably 85% or more, and most preferably 90% or more are preferable because they exhibit a very beautiful whiteness without dullness. A bluish index (color tone b value) determined from the white polyester layer (A) side of 0 or less, more preferably -0.5 or less, and most preferably -1 or less has a bluish tinge. It is preferable because it shows excellent whiteness.

The optical density of the white laminated polyester film of the present invention is not more than 0.1 at a thickness of 100 μm.
It is preferably from 6 to 2.0, more preferably from 0.8 to 1.8. When the optical density is less than 0.6, the back side of the film is transparent because the concealability of the film is small, which is not preferable. Further, the optical density is 2.
To exceed 0, a large amount of particles must be contained, and the strength of the film may be weak, which is not preferable.

Further, the white laminated polyester film of the present invention has a surface glossiness measured from the white polyester layer (A) side of preferably 45% or more, more preferably 50% or more, and most preferably 60% or more. Is excellent in smoothness, can form a high-definition image when used as a base material of a receiving sheet, and can give a higher quality image.

In the present invention, the thickness of the white laminated polyester film is not particularly limited.
Those having a range of 0 to 500 μm, preferably about 20 to 300 μm are preferable because they have excellent handling properties in practical use as a receiving sheet substrate. The thickness of the white polyester layer (A) is preferably 0.5 to 50 μm, more preferably 1 to 25 μm.
When the lamination thickness is smaller than the above range, whiteness and bluish color tend to decrease. On the other hand, if it is larger than the above range, the cost is increased and the effect of the laminated structure is reduced, which is not preferable.

Next, some examples of the method for producing the white laminated polyester film of the present invention will be described.
It is not limited only to such an example.

Regarding the method for producing a white laminated polyester film, in a composite film forming apparatus having an extruder (A) and an extruder (B), a polyester chip and an inorganic fine particle master chip are mixed with inorganic fine particles of 1 to 35%. % By weight and thoroughly vacuum dried.
Feed to extruder (A) heated to ~ 300 ° C. Further, for laminating the white polyester layer (B), the polyester chips and the inorganic fine particles and / or the thermoplastic resin incompatible with the polyester are mixed so as to be 1 to 35% by weight and sufficiently vacuum-dried. Is supplied to the extruder (B), and laminated in such a manner that the polymer of the extruder (A) comes to the surface layer (one side) or both surface layers (both sides) of the polymer of the extruder (B) in the T-die composite die. To obtain a molten laminated sheet.

The melted laminated sheet was subjected to a surface temperature of 1
On a drum cooled to 0 to 60 ° C., it is tightly cooled and solidified by static electricity to produce an unstretched film. The unstretched film is guided to a group of rolls heated to 80 to 120 ° C., stretched 2 to 5 times in a longitudinal direction (longitudinal direction, that is, a direction in which the film advances), and cooled by a group of rolls of 20 to 30 ° C.

Subsequently, the film stretched in the longitudinal direction was guided to a tenter while grasping both ends of the film with clips, and was then fed to a tenter.
The film is horizontally stretched in a direction perpendicular to the longitudinal direction in an atmosphere heated to 0 ° C.

The stretching ratio is 2 to 5 times in each of the vertical and horizontal directions, and the area ratio (longitudinal stretching ratio × lateral stretching ratio) is preferably 6 to 20 times. If the area magnification is less than 6 times, the whiteness and mechanical properties of the obtained film become insufficient, and if it exceeds 20 times, the film tends to be easily broken during stretching.

In order to impart flatness and dimensional stability to the biaxially stretched film thus obtained, 150
After heat-setting at ２３０230 ° C., the mixture is gradually cooled, cooled to room temperature, and wound up to obtain the white laminated polyester film of the present invention.

The white laminated polyester film thus obtained is excellent in bluish whiteness and can give a high-quality image when used as a base material of a receiving sheet based on whiteness. It is suitably used as a base material of a receiving sheet used for various printing records such as ink jet, thermal transfer and offset printing.

[0056]

[Method for measuring and evaluating characteristics] The characteristic values used in the present invention are based on the following evaluation methods and evaluation criteria.

(1) Average particle size of inorganic fine particles Transmission electron microscope HU-12 type (manufactured by Hitachi, Ltd.)
The cross section of the white polyester layer (A) or the white polyester layer (B) was obtained from a cross-sectional photograph obtained by observing the cross section at 3,000 to 200,000 times.

That is, the particle portion of the cross-sectional photograph is marked, and the particle portion is subjected to image processing using a Hi-Vision image analysis processor PIAS-IV (manufactured by Pierce Co., Ltd.). The average diameter when the particles were converted into a perfect circle was calculated and defined as the average particle diameter of the inorganic fine particles.

(2) Inflection Point, Peak Reflectance, and Average Reflectance The white laminated polyester film was measured in a range of 350 to 700 nm using a broadband self-recording spectrophotometer U-3410 (manufactured by Hitachi, Ltd.). From the total light reflectance curve. First, the presence or absence of a convex inflection point is visually determined from the total light reflectance curve in the range of 350 to 500 nm,
The reflectance at the position of the inflection point was defined as the peak reflectance. When there was no convex inflection point, the highest value of the total light reflectance in the range of 350 to 500 nm was defined as the peak reflectance. In addition, the average value of the total light reflectance in the range of 500 to 700 nm was obtained and defined as the average reflectance.

(3) Whiteness According to JIS L-1015, U white manufactured by Shimadzu Corporation
It measured using V-260. Wavelength 450nm and 5
Assuming that the reflectance at 50 nm is B% and G%, respectively.
Whiteness is represented by the following equation.

Whiteness (%) = 4B-3G (4) Blueness index (color tone b value) For a white laminated polyester film, JI was measured using a spectral colorimeter SE-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.).
S Measured under the optical conditions according to Z-8722, JIS
It was determined as a color difference b according to K-7105. The smaller the measured value, the better the blue tint.

(5) Opacity The optical density (OD) was determined and measured using an optical densitometer TR927 (manufactured by Macbeth). The larger the measured value,
High concealability.

(6) Glossiness Digital goniogloss meter UGV-5B (Suga Test Instruments Co., Ltd.)
Was measured according to JISZ-8741. The measurement conditions were an incident angle of 60 ° and a light receiving angle of 60 °.

(7) Print clarity The following coating liquid for forming a receptor layer was applied to one surface of the white laminated polyester film of the present invention with a gravure coater so that the thickness after drying was 0.1 μm. After drying for a minute, a receiving sheet for thermal transfer recording was obtained.

"Receptive layer forming coating liquid" (A) Modified polyolefin: urethane modified polyethylene aqueous dispersion (urethane modified ratio = 20% by weight, emulsified by heating in aqueous ammonia solution to form an aqueous dispersion) B) Antistatic agent: phosphate-based ionic polymer aqueous dispersion (acid phosphooxy (polyoxyethylene glycol) monomethacrylate previously neutralized with potassium hydroxide (the number of repeating units of oxyethylene glycol n =
5) / butyl acrylate / acrylic acid 70/25 /
Emulsion polymerized at a ratio of 5 (% by weight). (A molecular weight = about 150,000) (A) / (B) were mixed at a solid content weight ratio of 50/50, and diluted with water to a solid content concentration of 3%.

Next, as a color printer, "Professi
onal Color Point 2 "(manufactured by Seiko Electronic Industry Co., Ltd.),
Using a dedicated CH705 (yellow, magenta, cyan, manufactured by Seiko I Supply Co., Ltd.) as a thermal transfer ink ribbon, a test pattern of four gradations was printed on the above-mentioned receiving sheet.

Then, the image clarity of the printed surface was visually determined, and the following four grades were evaluated. ○ The above was regarded as good.

A: The whole image is very clear and excellent.

：: clear image, good

Δ: The non-printed surface is slightly yellowish, and the image clarity is poor.

×: The non-printed surface is yellowish, the image has a dark impression as a whole, and the image clarity is completely poor.

[0072]

The present invention will be described with reference to the following examples and comparative examples, but the present invention is not limited to these examples.

Example 1 A polyethylene terephthalate (hereinafter abbreviated as “PET”) chip was provided with 14% by weight of anatase type titanium oxide fine particles having an average particle diameter of 0.3 μm, and a fluorescent whitening agent “OB”
The material to which 0.12% by weight of -1 "(manufactured by Eastman) was added was vacuum-dried at 180 ° C for 3 hours, and then extruded (A).
And melted at 285 ° C. by a conventional method and introduced into a T-die composite die.

On the other hand, 10% by weight of polymethylpentene (hereinafter abbreviated as “PMP”) was added to the PET chip, and 1% by weight of polyethylene glycol having a molecular weight of 4000 (hereinafter abbreviated as “PEG”) as a compatibilizer. % Was dried at 180 ° C. for 3 hours under vacuum, then supplied to an extruder (B), melted at 285 ° C. by a conventional method, and the white polyester layer (A) was turned into a white polyester layer (T) in a T-die composite die. A laminated melt sheet obtained by laminating both surface layers of B) was obtained. The laminated melt sheet was tightly cooled and solidified by an electrostatic charge method on a cooling drum maintained at a surface temperature of 25 ° C. to obtain an unstretched film.

Subsequently, the unstretched film is treated according to a conventional method.
The film was stretched 3.2 times in the longitudinal direction by using a roll group heated to 8 ° C., and cooled by a roll group at 25 ° C. Further, the stretched film was guided to a tenter and stretched 3.4 times in a direction perpendicular to the longitudinal direction in an atmosphere heated to 125 ° C. Thereafter, the film was heat-set at 220 ° C. in a tenter, uniformly cooled, and then wound up. The white polyester layer (A) had a thickness of 5 μm and the white polyester layer (B) had a thickness of 90 μm.
A white laminated polyester film of 0 μm was obtained.

The properties of the white laminated polyester film thus obtained are as shown in Table 1. The white laminated polyester film was excellent in bluish whiteness, exhibited cushioning properties, and was highly flexible.

Example 2 Of the raw materials supplied to the extruder (A) of Example 1, the added amount of the anatase type titanium oxide fine particles was 12% by weight, and the raw material supplied to the extruder (B) was a PET chip. A white laminated polyester film was obtained in the same manner as in Example 1, except that 14 wt% of anatase type titanium oxide fine particles having an average particle diameter of 0.3 μm were used.

The properties of this white laminated polyester film are as shown in Table 1, and were excellent in bluish whiteness and hiding properties.

Examples 3 and 4 On the basis of Examples 1 and 2, the raw materials supplied to each extruder (A) were the same as those in Example 1 except that the amount of anatase type titanium oxide added was 7% by weight. A white laminated polyester film was obtained in the same manner as in Examples 1 and 2.

As shown in Table 1, the properties of this white laminated polyester film are excellent in each property, particularly excellent in bluish whiteness, excellent in smoothness (gloss), and extremely excellent in clarity of a printed image. there were.

Example 5 Of the raw materials supplied to the extruder (A) of Example 1, an average particle diameter of 0.2 μm was used instead of the anatase type titanium oxide fine particles.
A white laminated polyester film was obtained in the same manner as in Example 1 except that barium sulfate fine particles of m were used and the addition amount was 18% by weight.

As shown in Table 1, the properties of this white laminated polyester film were excellent in each property, and particularly excellent in bluish whiteness.

Example 6 Of the raw materials supplied to the extruder (A) of Example 2, an average particle size of 0.5 μm was used instead of the anatase type titanium oxide fine particles.
A white laminated polyester film was obtained in the same manner as in Example 2 except that calcium carbonate fine particles of m were used and the addition amount was 7% by weight.

As shown in Table 1, the properties of this white laminated polyester film were excellent in each property.

Comparative Example 1 As a raw material supplied to the extruder (A) of Example 1, PET was used.
Except that a chip containing only 14% by weight of anatase-type titanium oxide fine particles having an average particle diameter of 0.3 μm was used,
A white laminated polyester film was obtained in the same manner as in Example 1.

As shown in Table 1, the characteristics of this white laminated polyester film were as follows:
There was no convex inflection point between 00 nm, and the whiteness, the bluish index, and the sharpness of the printed image were poor.

Comparative Example 2 As a raw material supplied to the extruders (A) and (B) of Example 1, a PET chip obtained by adding only 14% by weight of anatase type titanium oxide fine particles having an average particle diameter of 0.3 μm to a PET chip was used. Otherwise, a white polyester film having a thickness of 100 μm was obtained in the same manner as in Example 1.

The surface of this white polyester film was yellowish, and as shown in Table 1, was particularly poor in whiteness, blueness index and sharpness of a printed image.

Comparative Example 3 Example 1 was repeated except that the amount of the optical brightener added was 0.003% by weight among the raw materials supplied to the extruder (A) of Example 1.
A white laminated polyester film was obtained in the same manner as described above.

The properties of this white laminated polyester film were inferior to each property as shown in Table 1.

Comparative Example 4 A white laminated polyester film was produced in the same manner as in Example 1 except that the amount of the fluorescent whitening agent added to the extruder (A) of Example 1 was changed to 3% by weight. Obtained.

This white laminated polyester film is yellowish due to the coloring of the fluorescent whitening agent itself, and its properties are inferior in whiteness, blueness index and clearness of a printed image as shown in Table 1. Was something.

Comparative Example 5 As a raw material supplied to the extruder (B) of Comparative Example 1, PET was used.
A chip was prepared by adding 14% by weight of anatase-type titanium oxide having an average particle diameter of 0.3 μm and 0.02% by weight of the same fluorescent whitening agent used in Example 1.
A white laminated polyester film was obtained in the same manner as in Comparative Example 1.

As shown in Table 1, the properties of this white laminated polyester film were inferior to each property.

[0095]

[Table 1]

[0096]

The white laminated polyester film of the present invention is a two or more white laminated polyester film having at least a white polyester layer (A) and a white polyester layer (B), wherein the white polyester layer (A) side Has at least one convex inflection point between 350 and 500 nm in the total light reflectance curve in the range of 350 to 700 nm measured from, and the peak reflectance at the position of the inflection point is 500 to 700 nm. 5% or more higher than the average reflectance in the range of, and when used as a base material of a receiving sheet based on whiteness, by exhibiting a bluish whiteness and smoothness to a high degree, Can be given.

Since the white laminated polyester film of the present invention has the above-mentioned excellent properties, it is suitably used as a base material of a receiving sheet used for various printing records such as ink jet, thermal transfer and offset printing.

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 4F100 AA01A AA01C AA21 AA21H AK01B AK03B AK41A AK41B AK41C AK42 AK62B AK66B BA02 BA06 BA10A BA10C BA13 J13C CA13B CA13C J01B EH20B00 J38 GB YY00A YY00C 4J002 BB032 BB122 BB172 CF031 CF041 CF051 CF061 CF071 CF081 DD037 DE107 DE137 DE147 DE237 DE247 DG017 DG047 DH047 DJ017 DJ027 DJ037 DJ057 FD017 FD206 GF00 GT00

Claims (9)

[Claims] 1. A white laminated polyester film having two or more layers having at least a white polyester layer (A) and a white polyester layer (B), and having a range of 350 to 700 nm measured from the white polyester layer (A) side. The total light reflectance curve has at least one convex inflection point between 350 and 500 nm, and the peak reflectance at the position of the inflection point is 5% of the average reflectance in the range of 500 to 700 nm. A white laminated polyester film characterized by being larger than the above. 2. The white laminated polyester film according to claim 1, wherein the average reflectance in the range of 500 to 700 nm measured from the white polyester layer (A) side is 85% or more. 3. The white laminated polyester film according to claim 1, wherein at least the white polyester layer (A) contains a fluorescent whitening agent. 4. The white polyester layer (A) and the white polyester layer (B) contain a fluorescent whitening agent, and the content (% by weight) of the whitening agent in the white polyester layer (A) is reduced. The white laminated polyester film according to any one of claims 1 to 3, wherein the amount is larger than that in the white polyester layer (B). 5. The white polyester layer (A) contains inorganic fine particles, and the white polyester layer (B) contains fine air bubbles. 2. The white laminated polyester film according to item 1. 6. The white laminated polyester film according to claim 5, wherein the white polyester layer (B) contains a thermoplastic resin incompatible with the polyester. 7. The white laminated polyester film according to claim 6, wherein the thermoplastic resin is a polyolefin. 8. The white polyester layer (A) and the white polyester layer (B) contain a polyester resin and inorganic fine particles as main components, and the content (% by weight) of the inorganic fine particles in the white polyester layer (A). 5 is smaller than that in the white polyester layer (B). The white laminated polyester film according to any one of claims 1 to 4, wherein 9. A three-layer laminated structure wherein the core layer is a white polyester layer (B) and both surface layers are polyester layers (A). 2. The white laminated polyester film according to claim 1.